Silixane bond-containing compounds include polyorganosiloxanes, such as for example, silicone resin, silicone rubber, etc. A good deal of the siloxane bond-containing compound is conventionally discarded in the form of waste matters due to the combination failure during processing step, scraps formed in finishing step, or useless materials from a variety of industrial areas. Such a discarded silicone resin or silicone rubber can hardly be re-used because it's reclamation is almost impossible. Furthermore, since there have not developed as yet any effective cleavage methods for the discarded silicone resin and rubber, they are usually left untreated. Accordingly, processing factories have great difficulties to treat the wastes.
Chemical cleavage methods for siloxane bond-containing compound include decompositions by heat, acid, or alkali. Among those methods, a process for producing alkali metal trimethylsilanolate by heating hexamethyldisiloxane in the presence of an alkali metal hydroxide or alkoxide, as depicted in the following reaction scheme 1, can be exemplified as a related one to the process according to the present invention (see, J. F. Hyde et al, J Am. chem. Soc., 75, 5615, 1953; W. S. Tatlock and E. G. Rochow, J. Am. Chem. Soc., 72, 528, 1950).
Reaction Scheme 1 EQU (CH.sub.3).sub.3 Si!.sub.2 O+ROM.revreaction.(CH.sub.3).sub.3 SiOM+(CH.sub.3).sub.3 SiOR
in which
R represents hydrogen atom or alkyl, and PA1 M represents Na, K or Li. PA1 R' represents methyl or ethyl.
In addition, as depicted in the following reaction scheme 2, a process wherein potassium or sodium siloxanediolate is produced through the cleavage of cyclodiorganylsiloxane or straight polydiorganylsiloxane having a high molecular weight by potassium hydroxide or sodium hydroxide in the presence of a primary alcohol such as methanol, ethanol, etc. is disclosed in T. Takiguchi and M. Skural, Kogyo Kagaku Zassi, 63, 1476, 1960; W. Noll, Chemie und Technologie der Silicone, Verlag Chemie, Weinheim, 1968; A. Stock and C. Somieski, Ber., 52, 595, 1919; J. F. Hyde, J. Am. Chem. Soc., 75, 2166, 1953; and K. A. Andrianov and M. A. Sipyagina, Izv. Akad. Nauk SSSR, Neorg. Mat., 4, 2016, 1968. ##STR1## in which M represents Na or K, and
In the alkali-decomposition method as mentioned above, however, it is difficult to control the reaction since a primary alcohol such as methanol, ethanol, etc. is used as a decomposition facilitator. Also, according to this method, silica combined as a filler may not efficiently be recovered; the cleavage yield is low; and the molecular weight of the decomposition product is high.
It is described in the above alkali-decomposition method that secondary or tertiary alcohols can be used during the cleavage in addition to primary alcohols. However, since it is also described therein that "Secondary alcohols react with siloxanes in the presence of KOH or ROK more slowly than do primary alcohols, while tertiary alcohols are completely unreactive", the technical concept of the existing alkali-decomposition method is quite different from that of the present invention.